diff --git a/.isort.cfg b/.isort.cfg
index 466932b..caad3a6 100644
--- a/.isort.cfg
+++ b/.isort.cfg
@@ -9,4 +9,4 @@ line_length=88
 known_odoo=odoo
 known_odoo_addons=odoo.addons
 sections=FUTURE,STDLIB,THIRDPARTY,ODOO,ODOO_ADDONS,FIRSTPARTY,LOCALFOLDER
-known_third_party=requests,simplejson
+known_third_party=requests
diff --git a/mail_private/tests/test_js.py b/mail_private/tests/test_js.py
index 1bee5dc..d170c5e 100644
--- a/mail_private/tests/test_js.py
+++ b/mail_private/tests/test_js.py
@@ -22,7 +22,9 @@ class TestUi(odoo.tests.HttpCase):
 
         env = Environment(self.registry.test_cr, self.uid, {})
         partners = env["res.partner"].search([])
-        new_follower = env["res.partner"].search([("name", "ilike", "Ja")])
+        new_follower = env["res.partner"].search(
+            [("name", "ilike", "Ja"), ("email", "!=", False)]
+        )
         for partner in partners:
             partner.message_subscribe(new_follower.ids, [])
 
diff --git a/mailgun/models/ir_config_parameter.py b/mailgun/models/ir_config_parameter.py
index 57d7eac..e318dd8 100644
--- a/mailgun/models/ir_config_parameter.py
+++ b/mailgun/models/ir_config_parameter.py
@@ -1,10 +1,15 @@
 import logging
 
 import requests
-import simplejson
 
 from odoo import api, models
 
+try:
+    import simplejson as json
+except ImportError:
+    import json
+
+
 _logger = logging.getLogger(__name__)
 
 
@@ -23,6 +28,6 @@ class IrConfigParameter(models.Model):
             res = requests.put(url, auth=("api", api_key))
             if (
                 res.status_code == 200
-                and simplejson.loads(res.text)["domain"]["state"] == "active"
+                and json.loads(res.text)["domain"]["state"] == "active"
             ):
                 self.sudo().set_param("mailgun.verified", "1")